A fluororesin such as polytetrafluoroethylene, a tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer or an ethylene/tetrafluroethylene copolymer, has excellent characteristics in heat resistance, chemical resistance, water resistance, oil resistance, weather resistance, aging resistance, gas barrier properties, fuel barrier properties, releasing properties, non-stickiness, stain resistance, colorant adhesion resistance, non-elution properties, etc. and thus is used in various fields such as the semiconductor industry, aircraft and automotive industry, food manufacturing industry, medical industry, etc.
In the above applications, in order to make up for deficiency in mechanical properties such as wear resistance, toughness, flexibility, etc. or high costs, such an attempt has been made that a fluororesin is made to be a laminate with another general-purpose resin material, etc.
However, a fluororesin is generally poor in adhesion to another material, and if it is laminated with another resin material as it is, it is difficult to obtain a strong interlayer adhesion. Further, a fluororesin generally has a high molding temperature as compared with other resin materials, whereby there is a problem such that many other resin materials cannot withstand the molding condition of the fluororesin.
In order to solve such problems, Patent Document 1 proposes a multilayer laminate containing a laminate wherein a layer made of a fluororesin having functional groups such as acid anhydride groups (—CO—O—CO—) and having a melting point of from 120 to 230° C., and a layer made of a thermoplastic resin having functional groups capable of reacting with the functional groups of the fluororesin to form chemical bonds, are directly bonded.
The fluororesin disclosed in Patent Document 1 has functional groups such as acid anhydride groups, whereby its adhesion to another material is improved. In addition to this, the thermoplastic resin has specific functional groups, so that the adhesive functional groups and the functional groups of the thermoplastic resin will be reacted to form chemical bonds at the time of lamination, whereby the interlayer adhesion is said to be further enhanced. Further, this fluororesin has a low melting point and therefore can be molded at a molding temperature at which the thermoplastic resin can withstand.
However, this fluororesin is insufficient in elongation deformation processability and thus has a problem such as unevenness in thickness or wrinkles due to thinning, or non-uniformity of bubble diameters, when subjected to mold processing accompanying elongation deformation (such as blow molding, inflation molding, foam molding or film forming).